Index and table drive means for a machine tool

ABSTRACT

A SINGLE DRIVE AND CONTROL MEANS IS SELECTIVELY ENGAGEABLE TO PROVIDE EITHER RECTILINEAR MOVEMENT TO THE TABLE BASE OR ROTARY MOVEMENT OF AN INDEX TABLE CARRIED BY THE TABLE BASE.

United States Patent [72] Inventors EarlR.Lohneis [50] 90/1399, Milwaukee; 56 (R). 58 (R), 58 (B), 58 (C); 32/(lnquired) Richard E. Stobbe, Greenfield, Wis. 3978 References Cited UNITED STATES PATENTS 3.079,522 2/1963 McGarrell [2]] Appl. No. [22] Filed Jan. 19,1970 [45] Patented June 28,1971

3,125,796 3/1964 Brainardm". 3,175,190 3/1965 [73 Assignee Kearney 8; Treeker Corporation.

West Allis. Wis.

Primary Examiner-Arthur T. McKeon Attorneys-Thomas A. l-lauke, Donald E. Porter, William C. [54] gggg figgggi DRIVE MEANS FOR A Gleisner, Cyril M. l-lajewski and Robert c. Jones veno -11mm Figs.

90/ssRJ ABSTRACT: A single drive and control means is seleotively 90/56R engageable to provide either rectilinear movement to he table 8236 7/08, B23f 23/08 base or rotary movement of an index table carried by t e table base.

PATENTEDJUNZBIBYI 3587.390

sum 3 OF 5 Her 4- INVEN mp RL. RLOHNELS RICHARD ESTObBE PATENTED JUN28 I971 SHEET 5 OF 5 mass ass rants naive innxss son a siscams rs llilAClliGlROUND OF THE INVENTION The present invention relates to a single drive and control means for providing rectilinear movement to a table base and rotary movement to an index table of a machine tool, selectively.

Prior to this invention, the inclusion of an index table in the table base of a machine tool added greatly to the mechanical complexity and cost of the machine tool. This was due to the necessity of providing a separate driving means for both the supporting table base and the index table, which necessitated duplicating the numerous flexible couplings, fittings, hoses, wires, and the like required to energize and control the separate driving means for the index table and the separate driving means for the movable table base.

SUMMARY OF THE INVENTION it is, therefore, the object of the present invention to provide a simple, inexpensive means for providing rectilinear motion to a table base and rotary motion to the index table of a machine tool through the operation of a single drive and control means.

According to the present invention, there is provided to a machine tool having a bed supporting a table base for rectilinear movement along the bed. The table base includes at least one index table carried thereby and rotatably indexable about its own axis and relative to the table base on which it is supported. A single means comprising a common drive, a control means and a coupling means operable to engage the drive and control means to operate either the table base or index table selectively.

BlRiEF DESCRIPTION OF THE DRAWHNGS FIG. ll is a perspective view of a machine tool incorporating the features of the present invention;

FIG. 2 is a fragmentary, enlarged view in vertical section through the table base and supporting bed, taken in a plane along the line 2-2 of FIG. i and showing table 3d in the stationary or nonmovablc position and table MA in the rotating position;

lFlG. 3 is an end view of the table base showing the relationship of the input drive shafts for effecting X-axis movement of the table base and rotary motion of the index table.

FIG. d is a developed view of the drive mechanisms taken in the plane represented by the line M in FIG. 3.

FIG. 5 is an enlarged fragmentary side view of the checker valve and also showing the engagement of the shifting fork to the ring gear of the shittable gear mechanism.

FIG. s and dA are diagrammatic views of the hydraulic circuit depicting the various positions of an index table.

DESCWPTION OF THE PREFERRED EMBODIMENT Referring now to H0. ll, there is shown therein a machine tool of the type with which the present invention may be employed. Machine tool 110 includes a bed i2 which supports a vertical column H3. The vertical column 13 contains a pair of ways Ml on which is mounted a saddle 16, for vertical movement along the Y-axis relative to the column. Saddle 16 includes a second set of ways 17 on which is mounted for horizontal movement along the Z-axis, a spindle head lid. Spindle head 118 contains a tool spindle 20 in which is inserted metal working tool 2i. Tool spindle 24) is rotated by motor 22.

Machine tool bed i2 is provided with a pair of longitudinal ways 23, which support a table base 24 for horizontal movement along the X-axis in front of column l3 and spindle head id.

A lead screw 205 engages a nonrotatable nut (not shown) in spindle head iii and moves spindle head along the lands of the machine tool when the former is rotated. The lead screw may be rotated by any suitable means such as the electric motor 27. A rotary signal generator 2d, which may be of the photoelectric or electromagnetic type, is affixed to electric motor 27 to provide a series of pulses or signals corresponding to the rotation of the electric motor 27 to an automatic control means 30. Electric motor 27 and the other motors employed in machine tool it) may be energized and regulated by the automatic control means 30 connected to the machine tool it) by conduit 31. The automatic control means 30 includes a tape reader 32 which reads recorded data on punched tape 33 in a well-known manner to provide the operating control signals to the machine tool.

H6. 2 shows an embodiment of the present invention in which the table base 24 is provided with a pair of index tables 1% and MA. The inclusion of such a pair of index tables is desirable to permit the workpiece on one of the tables to be machined while the previously machined workpiece on the other index table is removed and a new workpiece is affixed to the table. Table base 24 is then moved or shuttled so that the new workpiece undergoes the machining operation while the previously machined workpiece is removed.

The index tables are each rotatably movable on the table base 2d about their own axis which extends through the table base and parallel to ways M and the Y-axis of machine tool 10 so that the workpiece may be rotated on the table base without the necessity of unclamping and reclamping the work piece to the table base. Such rotary motion of the index tables is in addition to the relative motion oli table base 24 and spindle head lid.

As shown in FIG. 2, the table base 2A is slidably mounted on ways 23 and moved along the ways by a lead screw 3% extending through nut 39, which is secured to the machine bed i2. Lead screw 35 is rotated in either direction by an electric motor d0, shown in FIG. 11, which is provided in a well-known manner with a rotary signal generator 42 to provide a series of pulses or signals corresponding to the number of rotations of motor M).

The construction and operation of table MA is the same as 34, so the following description of table 3d will apply to table MA.

index table 3d includes the flat disc portion d3 containing T slots 36. A column M extends downwardly from disc d3 along the axis of rotation of index table 343. Index table 3d is journaled in a collar 415 by means of an upper bearing as and a lower bearing d7. Collar 45 is, in turn, fitted in a sleeve Ad for axial movement in the sleeve, Such axial movement permits the raising and lowering of the index table 34 with respect to table base 24. Sleeve M is secured to a circular web member 53 formed in the table base 2d by means of screws d9.

Index table M is prevented from moving when it is in its lowermost position by operation of a toothed coupling 50. The toothed coupling 50 is famed of a pair of rings 5i and 52 having engaging teeth projecting from the opposing annular planes of the rings. When the teeth are engaged, as shown by table 3d, relative rotary motion between rings 511 and 52 is prevented. When the teeth are disengaged, as by raising ring 5 LA, as shown by the position of table 34A, relative rotation between the two rinm is permitted.

Ring 51 is mounted on the underside of disc d3 of index table 34 with its teeth extending downwardly so as to engage the upwardly extending teeth of ring 52 mounted on sleeve Ad.

The toothed coupling 50 also provides a means for accurately controlling the positioning of index table 3d. For this purpose, the number of teeth cut in the rings corresponds to the minimum indexing increment desired. For example, if it is desired to index table 343 every 5 of arc, '72 teeth are cut into each of the rings 51 and 52. Thus, teeth may be fully engaged only every 5 of rotation of index table 3d and accurate indexing of the table into these 5 increments is insured.

The peripheral surface 55 of index table M contains a limit switch actuator 56 which actuates limit switches 57 and 53 in a manner hereinafter described.

Index table M is indexed or rotatably moved by a motion translating means interposed between the table base 2d and the index table 34. Such motion translating means includes a ring gear 60 which is secured to the underside of the disc portion 33 of the table 34 adjacent the toothed coupling 503. Table base Ed has an idler gear assemblage 62 disposed between the two index tables 3 and MA. A carrier all is secured to the web members 53 and 53A of the table base 24 by screws 63.

The carrier 61 is provided with three in-line circular openings in which shafts 6d, 68 and 72 are rotatably supported. To this end shaft 64 is supported in the central opening in carrier 6 by bearings 65 and as; shaft 68 is supported in the lefthand opening, as viewed in FlG. 2, by bearings 69 and 7b; and shaft 72 is supported in the right-hand opening, as viewed in FIG. 2, by bearings 73 and 74. A spur gear IQ is mounted on the upper end of shaft 6 so as to engage both a gear 77, which is mounted on shaft db, and a gear 78, which is mounted on shaft 72. A ring gear 80 is mounted on the lower end of shaft d4 so as to engage with a gear in which is secured on a reduced inner end portion of a horizontal index drive shaft 85. index drive shaft 85 is rotatably supported at its rightward end by bearing b9 and 90 located in a support block $36, which is secured by screws 93 to the bottom of carrier at, as illustrated in FIG. 2. The left end of shaft 85 is rotatably supported in bearings 91 and 92, as shown in FIG. 3, located in the gear drive box dil. A driving sleeve 95 is secured to shaft by a key 96. Mounted on the right end of sleeve 95 is an index table drive gear 9% and mounted on the left end of sleeve 95 is an index locking gear 99. I

In normal operation, when rotary movement of index tables 34 or 34A is not desired, the index tables remain in the lowered position as depicted by the position of index table 34% in FIG. 2. Under this condition the index table drive shaft 55 is disconnected from motor dd by a shiftable gear assembly 2543 which will hereinafter be described. When motor 449 is disconnected from index table drive shaft 85, it is connected to drive the X-axis screw 32; and thereby move table base to the desired X-axis position. At this time shaft 85 and the idler gear assemblage 62 do not rotate while machine tool llilli is in its nonindexing mode of operation. This results in a more favorable torque to inertia ratio for the X-axis drive motor 43th. This also results in less wear in the mechanical parts of the index drive because the index drive is engaged only during the actual indexing movements of the tables 36 and 34A.

X-axis drive screw 33 is rotatably supported by a bearing 87 located in end surface 83 of the table base 24, as shown in FIG. 2, and a bearing it carried in a gear drive box M, as shown in MG. 6, which is secured to the outer surface of the table base 2 8 located at the other end of the table base 243. An X-axis drive gear W2 is secured to the left end of screw 38 by a key HM. The output shaft W3 of the DC drive motor 4b is provided with a ring gear MM which is keyed thereto.

The shiftable gear assembly 34, as shown in FIGS. 4 and 5, is provided with a locking plate 107 having an extending tubular sleeve portion 108. The locking plate W7 is provided with internal splines (not shown) which are slidably engaged with complementary splines KW that are formed on shaft Hi2. Shaft H2 is fixedly secured in the gear drive box Ail. A gear 114 is cam'ed for rotation relative to locking plate MP7 on the outer races of a pair of bearings HS and 111165. The bearings H5 and 116, in turn, are mounted on the extending sleeve portion 10b of the locking plate 1W7. Therefore, gear HM is free to rotate while the locking plate 11b7, coupled by its splines (not shown) with the complementary splines HM of stationary shafi H112, remains in its angular fixed position. Ring gear Kid is always in mesh with motor output gear HM so as to transmit power from the DC motor 40 to either the X-axis drive gear 102 or the index table drive gear W, selectively.

A shifting fork B24 is used to effect the axial movement of the shiftable gear assembly lid from its leftward position, as viewed in FIG. 5, where the shiftable gear assembly is engaged with the X-axis drive gear H02, to its rightward position where the shiftable gear assembly 343 is engaged with the index drive gear 98. The shifting fork 124i is secured to an actuating rod 126 of a hydraulic actuator assembly H23. The bifurcated extending end 1125 of the shifting forlr i124 engages either side of the index locking plate W7. Thus, when the hydraulic actuator assembly R28 is actuated, the shifting fork 1243 will move the shiftable gear assembly 23d axially along shaft H2 in one direction or the other.

F108. 4 and show the actuating rod E26 biased to the left which, in turn, effects the engagement of the gear lid, of shiftable gear assembly 8 3, with the X-axis drive gear 1102. When the actuating rod 126 is biased to the right, this will effeet the engagement of gear lid with the index table drive gear 913. Since the output gear MM of DC motor 40 is always engaged with gear lid of the shiftable gear assembly 34, the power output of motor 60 will be used to drive either the X- axis screw 3b or the index drive shaft d, selectively.

As shown in FIG. 5, the hydraulic actuator assembly 128 for effecting the selective drive engagement of the X-axis screw 38 or the index table drive shaft with the motor (W is comprised of a valve body 330 having three axial bores BR, and 336. The valve body I30 is ecured to the external surface of the gear drive box 41 with screws H2. The outer or leftward end of axial bores 1139 and R36 are closed by an end cap 338 which is secured with screws 1139 to the outer end of valve body 130. The actuating rod 12s extends outwardly from the shifting fork H2 3 through a suitable opening Mil of gear box M and through the axial bore 131 and outwardly through an opening of the outer end cap 138.

Slidably carried within the axial bores i135 and 136 are valve spools M7 and 148 respectively. Axial bores H35 and H36 in cooperation with the valve spools M7 and 1418 respectively, form checker valve assemblies H50 and 15H, respectively. Checker valves 150 and 15! regulate the raising and lowering of the index tables 3 3 and 34A, respectively. The construction and operation of checker valve E511 is the same as checker valve 150, so that the description of the construction and operation of the checker valve Eb will apply to checker valve E51. Axial bore 135 is divided by the spool 1457 into three subchambers 13$A, E358 and ll3C. There are five ports, H65, H66, 167, M8 and 169 provided which communicate with the axial bore 135 of the checker valve assembly 150. Selective admission of hydraulic fluid into the axial bore 1135 via these ports control the position of valve spool M7 and consequently the vertical movement of the index table 34.

As shown in FIG. 5, the leftwardly extending portion B3 of spool M7, passes through a bore RM formed in the end closure cap 113$. Secured on the extreme leftward end of spool portion 11% is a collar 1%. A sleeve H58 having a flange portion i139? is secured to actuating rod 1126 so that they move axially in unison. Sleeve 1% is carried for axial slidable movement in an enlarged diameter portion of the bore 131. The arrangement is such that an inner surface H62 of collar E56 abuts a surface 163 of flange R59. Therefore, as checker valve 115d is actuated to effect the movement of spool M7 to the right, as viewed in FIG. 5, the engagement of collar 156 with flange 1159 will efi'ect the rightward movement of actuating rod M26. The rightward movement of actuating rod 1126 will effect the movement of the gear lid of the shiftable gear member assembly H05, out of engagement with the X-axis drive gear W2 and into engagement with the index table drive gear 59$.

As shown in W68. 41 and 5, the actuating rod i126 is depicted in its extreme leftward position, which is the position it is in when the shifting forlr 1124 has effected the movement of the shiftable gear assembly b4 into engagement with the X- axis drive gear 102. Thus, the output of the common drive motor Ml is transmitted to the Xaxis drive screw, via ring gear 1M and drive gear R02, to effect the rectilinear movement of the table base in one direction or the other, depending upon the rotation of motor so.

When it is desired to connect the output of the common drive motor 4b to the index table drive gear 953 for effecting indexablc movement of either table 34 or 34A, hydraulic pres sure fluid will be supplied through port 16?, into subchamber 135A to exert a force on spool surface R71 to move the spool M7 rightwardly as viewed in FIG. 3. As spool M7 moves to the right, hydraulic fluid in subchamber 1338 will be drained through port the to an oil reservoir llflll, as shown in FIG. 6. The rightward movement of spool M7 will effect the shifting of ring gear lid from engagement with the X-axis drive gear 1102 into meshing engagement with the index table drive gear 90, to effect the rotation of index drive shaft 03 in one direction or the other, depending upon the rotation of motor 00. This is true because as the spool M7 moves to the right, its attached collar R50 will engage flange 159 of actuating rod HM to effect the axial movement of shifting fork TM and the shiftable gear assembly M which is connected to the bifurcated end Md of shifting fork ilMl.

When it is desired to disconnect the output of the common drive motor d0 from the index drive gear 90 and connect the output of the motor d0 t0 the X-axis drive gear 102, hydraulic pressure fluid will be supplied through port M7 to subchamber WOC, to apply a force to spool surfaces T73 and i7d. As hydraulic pressure fluid is supplied to subchamber 1133C it will flow through passage 173 formed in valve body 130 to supply pressure fluid to a chamber 1l77 formed by the bore M3 and the inner end of sleeve 150. The hydraulic pressure fluid in chamber 177 applies a force to end surface 170 of sleeve 11%. Since the combined surface areas of surfaces 173 and 1170 is greater than the area of surface I'M, a differential force will be exerted to effect the leftward movement of piston rod rss. The leftward movement of piston rod H26 will effect leftward movement of the shifting fork 124i, thereby shifting the sleeve lltliii to reconnect the ring gear 114 with the X-axis drive gear 102.

. The hydraulic circuit for driving the various components described is illustrated diagrammatically in FIGS. 6 and 6A and comprises a pump iflll connected to draw hydraulic fluid from the reservoir llflll. The output of the pump 1 is discharged into a pressure line 102 with the exhaust fluid being carried back to the reservoir by return line E03.

index table M is raised from the position shown in FIG. s to the position depicted in FIG. 0A by energizing solenoid l to actuate valve i055 to connect pressure line m2 to port 163 of checker valve 1150. The hydraulic pressure fluid will pass through port Th3 into subchamber ll ldA and exert a force on spool surface i'lll to effect the rightward movement of spool M7 as viewed in FIG. 3. When spool surface 171i moves past port ass, hydraulic pressure fluid will flow out of port H60 and into annular chamber iiflfl of table base 2d via fluid conduit iliih, as shown in FIG. 2. The hydraulic pressure fluid admitted to annular chamber llhfl acts on a radial flange we of the colla: did to effect upward movement of the collar, thereby elevating the index table 34. As the index table 34 is elevated, hydraulic pressure fluid will be exhausted from a chamber 193 located above radial flange 11%, via fluid conduit H91 through port M0 of checker valve assembly 1150. The fluid entering subchamber i358 via port 109 will pass out of drain port ass to the reservoir ifli. Also, as the spool M7 is moved to the right, the hydraulic fluid within subchamber 1135C will exhaust through internal passage 195 formed within the spool M7 to subchambcr i350 and, consequently, it will also exhaust through exhaust port 1st to return to reservoir 101.

As a prerequisite to the indexing of table 3d, to rotatably position the workpiece, table base 24 has to be located along ways 23 at any 001 inch position. The positioning of table base 2d at any 0.01 inch position, along the X-axia will insure the meshing of the index locking plate 107 with the X-axis drive gear i102 and consequently it will insure the meshing of ring gear llildl with the index table drive gear 90 and the meshing of index table ring gear 60 with gear 77 of the idler gear assembly as. If a wrong l t-axis distance is called for, for example one not at a 0.01 inch position, such as 20.022, the teeth of locking gear i107 and the teeth of the drive gear 102 will not be in position to meshingly engage and, therefore, gears will hang up. This will prevent the actuating rod 126 from moving all the way to the right and, therefore, will not allow spool M7 to move all the way to the right and, therefore, port 1168 will be blocked and pressure fluid entering port i163 will not be supplied to chamber Hi0 and consequently the index table 34 will remain in its lower position as depicted in FIG. s. Consequently the index table will not rise and the X-axis position called for will have to be checked and corrected so that a 0.0l position is commanded.

When the shiftable gear assembly is shifted between the two drive gears 00 and 1102 it is desirable to keep a fixed angular relationship between the rotor of the signal generator $22, which is connected to motor 410, and the two drive gears 00 and 102. To this end the locking plate 1107 is used to angularly lock one of the drive gears or I02 before it disengages the other.

As depicted in FIG. d, the lower portion locking plate R07 is in mesh with the index locking plate 09 when the actuating rod 1126 is in its leftward position. As the actuating rod 126 is moved to the right, it will be noted that the upper portion of locking plate 107 will engage and lock the X-axis drive gear 1102 in its angular position before the lower portion of locking plate becomes disengaged from the index locking plate 99. When the shiftable gear assembly is in its far right position, ring gear lid is in driving engagement with the index table drive gear 90. When the leftward movement of the shiftable gear assembly is effected by the movement of actuating rod 126, it will be noted that the lower section of locking plate 107 will engage and lock the index plate 90 in its angular position before the ring gear 1M becomes disengaged with the index table drive gear 90. Therefore the interaction of locking plate 107 with the X-axis drive gear R02 and. with the index locking plate 99 will insure that the signal generator 42 will be in a fixed angular relation with both the X-axis drive gear 1102 and the index table drive gear 90.

The index table 3d is lowered into table base 24 by deenergizing solenoid ll, valve will be spring returned to the position shown in FIG. s, to connect the pressure line m2 to port 167 of checker valve 150. Hydraulic fluid will pass through subchamber W3C and out of port 1169 to fluid conduit 1911 which is connected to annular chamber K93. The pressure fluid acting on the upper surface of the radial flange llM will force the index table 34 downwardly. As the index table 3 1 is moved downwardly, the hydraulic fluid below radial flange TM in annular chamber m9 is exhausted through conduit R00 to port ass of checker valve 150. The hydraulic fluid entering chamber 1135B will pass through drain port 166 to reservoir llflll.

For example, let it be assumed that the index table 34 has been stopped at the 20.000 X-axis position and that the index table has been elevated. When the index table 3d is fully elevated, limit switch 57 is actuated and operates to allow the DC motor 30 to drive the index table: 3d. The X-axis signal generator a2 is driven by motor 40 and is utilized to control the rotation of the index table 34. To this end, gear ratios are used so that one revolution of the signal generator an is equal to one degree of index table movement. When the motor d0 is connected to the X-axis drive screw 30, gear ratios are used so that one revolution of the signal generator 42 is equal to 0.1 inch of X-axis travel. If we desire to rotate the now elevated index table 34, 20, the signal generator d2 would have to be driven by motor 40 through 20 revolutions. One revolution of signal generator 42 equaling l of index table movement. To this end, the tape 33 would call for a new X-axis position of 22.000 inches. A new X-axis distance of 2.000 inches effects twenty revolutions of signal generator d2 since one tenth of an inch of X-axis travel called for by the tape 33 effects one revolution of signal generator 452.

After the necessary rotation, the index table 1% will be lowered. When the table is all the way down, limit switch 53 is actuated which operates to effect the next block of tape to be read. This is a miscellaneous function which counts the "X" position register back to where it started at the start of the index cycle. It is not necessary to move the signal generator d2, since the signal generator is in the same position as it was when it started the index cycle (20 signal generator revolutions will produce of indexing at the table). When moving the axis position register back, it is done at a faster feed rate than the normal X-axis feed rate travel, to save time. After the X-axis position register is counted back to its original position before the index cycle began, the control 30 is now ready to read the next command from the input tape.

Although the illustrative embodiment of the invention has been described in considerably detail for the purpose of disclosing a practical operative structure whereby the invention may be practiced advantageously, it is to be understood that the particular apparatus described is intended to be illustrative only and that the novel characteristics of the invention may be incorporated in other structural forms without departing from the spirit and scope of the invention as defined in the subjoined claims.

The principles of this invention having now been fully explained in connection with the foregoing description, we hereby claim as our invention:

We claim:

1. In a machine tool having table base supported for rectilinear movement along a supporting bed, said table base being provided with an index table supported by said table base for movement with it and for independent indexable movement relative to said table base;

a source of power;

a first drive means carried by the bed and operable to effect the rectilinear movement of said table base; a second drive means carried by said table base and operable to effect the indexable movement of said index table;

coupling means operable when actuated to connect said source of power to said first drive means or to said second drive means selectively; and,

control means operable to actuate said coupling means and said power drive means for effecting rectilinear movement of said table or indexing movement of said index table selectively.

2. in a machine tool having a bed supporting a table base for rectilinear movement along the bed, at least one index table carried by said table base and rotatably indexable about its axis;

power drive means operably connected to effect either the rectilinear movement of said table base or the rotary movement of said index table, selectively;

a first motion translating means located on said table base and operably connected to said bed to effect the rectilinear motion of said table base relative to said bed;

a second motion translating means carried by said table base and operably connected to said index table to effect the rotary motion of said index table;

coupling means operable to engage said power drive means with either said first or second motion translating means, selectively; and,

control means connected to said power drive means to regulate the operation of said power drive means;

whereby the rectilinear movement of said table base and the rotary movement of said index table may be selectively effected by operation of a single power drive.

3. In a machine tool according to claim 2 wherein said first motion translating means includes a screw operably mounted on said table base parallel to the direction of rectilinear movement of said table base; and,

a nut secured to said machine tool bed and operably connected to said screw.

4. in a machine tool according to claim 2 wherein said second motion translating means includes a gear secured to said index table in coaxial relationship therewith;

a gear transmission carried by said table base;

means to efi'ect engagement between said index table gear and said gear transmission; and,

a drive shafi connected to receive the input drive from said power drive means and transmit it to said gear transmission.

' 5. In a machine tool according to claim d wherein said coupling means includes a shiftable drive transmission operably disposed to engage said screw or said drive shaft selectively, said shiftable drive transmission being operably connected to receive the power input drive from said power drive means.

6. A machine tool according to claim 2 wherein said power drive means includes a motor.

7. A machine tool according to claim 2 wherein said control means includes a signal generator operative to provide a signal indicating the number of revolutions of said motor; and,

a position register connected to said signal generator and operable to indicate either the amount of rectilinear distance said table base traveled or the amount of rotation of said index table, selectively. 

